When you think of one thing that reminds you of another and so forth. Next thing you know, you're thinking of something so incredibly random, you forgot how you got there. Similar to surfing the web.
While brainsurfing, I forgot to call the childhoodfriend I planned to call, remembering what we used to do together, then ended up wondering what happened to our 5th grade time capsule, and wondering if anyone may have already dug it up.
Fogey/fogy /fougi/ sl. (early 18C+, orig. Scot) old-fashioned, stuck-in-the mud.
Person with old fashioned ideas which he is unwilling to change: Come to the disco and stop being such an old fogey!
You think me an old fogeyand an old tory, his thoughtful voice said. I saw three generations since O’Connel’s time. I remember the famine. Do you know that the orange lodges agitated for repeal of the union twenty years before O’Connel did or before the prelates of your communion denounced him as a demagogue? You fenians forget some things. (James Joyce, Ulysses. Penguin Books,1992. p. 38)